Method for manufacturing thin film semiconductor device and method for forming resist pattern thereof

Abstract

A method for manufacturing a thin film semiconductor device is provided which is capable of achieving simplification of manufacturing processes and of improving alignment accuracy without using a plurality of alignment masks. An alignment pattern is formed by using a resist layer having a plurality of regions each having a different film thickness corresponding to each of a plurality of patterns produced using a halftone mask having a halftone exposure region as a photomask and by forming a light transmitting portion to be an aperture pattern and by etching an underlying silicon layer. By having an underlying silicon layer exposed and implanting ions into an entire resist layer, only a main pattern region is doped with the ions.

1. A method for manufacturing a thin film semiconductor device comprising the steps of:
 forming an underlying silicon layer on a surface of a substrate;  
 forming on a surface of said underlying silicon layer using a photomask having a halftone region, a resist pattern comprising a resist-removed region and a plurality of kinds of resist regions each being different from each other in thickness;  
 forming an alignment pattern on said underlying silicon layer by etching said resist-removed region using said resist pattern as a mask;  
 removing a kind of the resist region having a smallest film thickness in said resist pattern to expose an underlying layer, and  
 forming another pattern different from said alignment pattern using a remaining resist pattern as a mask after removing said kind of resist region having said smallest film thickness.  
 
     
     
       2. The method for manufacturing the thin film semiconductor device according to  claim 1 , wherein the step of forming said another pattern different from said alignment pattern on said underlying silicon layer includes a step of ion implantation using said remaining resist pattern as a mask. 
     
     
       3. The method for manufacturing the thin film semiconductor device according to  claim 1 , wherein the step of forming said another pattern different from said alignment pattern on said underlying silicon layer includes a step of etching using said remaining resist pattern as a mask. 
     
     
       4. The method for manufacturing the thin film semiconductor device according to  claim 1 , wherein a transparent insulating substrate is used as said substrate. 
     
     
       5. A method for manufacturing a thin film semiconductor device comprising the steps of:
 forming an underlying silicon layer on a surface of a substrate;  
 forming, on a surface of said underlying silicon layer, using a photomask having a halftone region, a resist pattern comprising a resist-removed region and a plurality of kinds of resist regions each being different from each other in thickness;  
 forming an alignment pattern on said underlying silicon layer by etching said resist-removed region using said resist pattern as a mask;  
 removing a kind of the resist region having a smallest film thickness in said resist pattern by an ashing method to expose an underlying layer,  
 and  
 forming another pattern different from said alignment pattern using a remaining resist pattern as a mask after removing said kind of resist region having said smallest film thickness by performing said ashing method.  
 
     
     
       6. The method for manufacturing the thin film semiconductor device according to  claim 5 , wherein the step of forming said another pattern different from said alignment pattern on said underlying silicon layer includes a step of ion implantation using said remaining resist pattern as a mask. 
     
     
       7. The method for manufacturing the thin film semiconductor device according to  claim 5 , wherein the step of forming said another pattern different from said alignment pattern on said underlying silicon layer includes a step of etching using said remaining resist pattern as a mask. 
     
     
       8. The method for manufacturing the thin film semiconductor device according to  claim 5 , wherein a transparent insulating substrate is used as said substrate. 
     
     
       9. A method for forming a resist pattern on a surface of an underlying silicon layer formed on a surface of a substrate comprising the steps of:
 forming a resist layer by coating with a photoresist;  
 forming an alignment pattern portion, a main pattern portion used in a subsequent process following formation of said alignment pattern portion, a light transmitting mask region, a halftone exposure region, and a light intercepting region on a photomask used for formation of a pattern on said resist layer; and  
 performing an exposure operation on the formed resist layer using said photomask and performing a development operation to produce a plurality of resist regions each having a different thickness and at least one resist-removed region.  
 
     
     
       10. The resist pattern forming method according to  claim 9 , wherein said at least one resist-removed region is produced by said light transmitting mask region as an aperture pattern.